I am not really happy with it so far. My mileage went down after I installed it. I am hoping this will change as it is used. I did nothing else to it and on its first trip of 400 miles my mileage went from 9.7 to 7.8. Ford E-450 V-10 Jayco RV Redhawk. If it doesn't improve I will put the stock one back in service and remove the K&N Air Filter.